The Structure Module defines the major structural elements for XHTML. These elements effectively act as the basis for the content model of many XHTML family document types. The elements and
attributes included in this module are:

This module is the basic structural definition for XHTML content. The html element acts as the root element for all XHTML Family Document Types.

Note that the value of the xmlns attribute is defined to be "http://www.w3.org/2002/06/xhtml2". Also note that because the xmlns attribute is treated specially by XML namespace-aware parsers [XMLNAMES], it is legal to have it present as an attribute of each element. However, any time the xmlns attribute is used in the context of an
XHTML module, whether with a prefix or not, the value of the attribute shall be the XHTML namespace defined here.

This attribute specifies the location of one or more meta data profiles, separated by white space. For future extensions, user agents should consider the value to be a list even though this
specification only considers the first URI to be significant. Profiles are discussed in the section on meta data.

The head element contains information about the current document, such as its title, keywords that may be useful to search
engines, and other data that is not considered document content. The default presentation of the head is not to display it; however that can be overridden with a stylesheet for special purpose use.
User agents may however make information in the head available to users through other mechanisms.

The title element is used to identify the document. Since documents are often
consulted out of context, authors should provide context-rich titles. Thus, instead of a title such as "Introduction", which doesn't provide much contextual background, authors should supply a title
such as "Introduction to Medieval Bee-Keeping" instead.

For reasons of accessibility, user agents must always make the content of the title element available to users. The mechanism for doing so depends on the user agent (e.g., as a caption, spoken).

Titles may contain entity references (for accented characters, special characters, etc.), but may not contain other markup (including comments).
Example:

The body of a document contains the document's content. The content may be presented by a user agent in a variety of ways. For example, for visual browsers, you can think of the body as a canvas
where the content appears: text, images, colors, graphics, etc. For audio user agents, the same content may be spoken.